Multi-position switching systems



March 18, 1958 TO LAST TARGET OF PRECEDING TUBE? Filed May 17, 1955 ET TO SPADE RESISTORS Es R /R OF NEXT TUBE 7 V5 A RI I VT RT gRg RT gR R1- R R R2 T|9 TIO TH T|2 30 ,0

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R gR R gR R 5R5 R B R 2 TIO Tll Tl2 p GIO en G12 619 \J 1 21 K v EVEN GRIDS) FLIP-FLOP INVENT0R.- PULSE JOHN R. BETHKE GENERATOR BY PULSE 7 INPUT ATTORNEY Stats MULTI-POSITION SWITCI-HNG SYSTEMS John R. Bethke, Paoli, Pa., assignor to Burroughs Corporation, Detroit, Mich a corporation or Michigan This invention relates to multi-position switching or distributor circuits using electron discharge devices of the magnetron beam switching type.

In the complex circuitry of missile guidance systems, telemetering links, computers, and coding equipment, the need for precise and rapid switching or signal distribution is serious. As circuits become more complex, the number of positions needed in various switches or distributors grows very rapidly. Magnetron beam switching tubes perform this precise and rapid switching very well. However, physical factors limit the maximum number of switching positions per tube to about ten. It becomes advantageous to connect magnetron beam tubes in cascade so that a switching sequence will advance through the separate positions of each tube in succession. Since the time relationship of contacts for sequential switching positions often is a critical factor, this switching transition must proceed between tubes as smoothly as it does between positions within a tube.

In the system embodying this invention the beam is scanned through the output positions of a first tube after which the beam is extinguished in this first tube and reformed in a succeeding tube where a subsequent scanning cycle takes place.

An object of this invention is to provide an improved multiple position electronic switching system using a plurality of beam switching tubes.

A further object of this invention is to utilize the number of output positions of each beam switching tube efii-,

ciently in a pulse distributor or switching circuit.

Another object of this invention is to produce a series of cascaded tubes with a plurality of sequential switching positions wherein the transition from one switching tube to the next is efiiciently accomplished to afiord stable switching.

An additional object of this invention is to produce an improved circuit for transferring a beam switching sequence from a selected position of a first beam switching tube to a selected position of a succeeding beam switching tube.

One type of discharge device which may be utilized in this invention is a magnetron beam switching tube shown and described in an article entitled A New Beam Switching Tube, published in Electronic Design of January 1954. Such a tube also is the subject of U. S. Patent No. 2,721,955 entitled Multi-Position Beam Tube by S. P. Fan et al. This magnetron beam switching tube has an elongated axial cathode and several circular concentric arrays of other electrodes around it. On a first or smallest radius from the cathode is an array of evenly spaced spade electrodes. These spade electrodes are of approximately U-shaped cross-section with their convex surfaces facing the cathode. These spades serve to form a beam within the tube and to hold the beam in place so that it partly impinges on other electrodes. In line with one side of each spade and on a slightly larger radius is an array of switching electrodes.

W Patented Mar. 18, 1958 These switching electrodes are elongated rods and are aligned parallel to the axial cathode. They serve to disturb the stable beam holding function of an associated spade and to cause the beam to switch over to the next position in which it can be stably held.

On the next larger or outside radius is an array of L- shaped target electrodes. One arm of each L is arcuate and positioned on the circumference in line with one of the open spaces btween two spades. The radial arm of each L extends inwardly toward a spade and may actually project slightly into the concave space or cavity of that spade. One of the switching electrodes is positioned between a spade on the other side of the space between spades and the end of the arcuate arm of the L- shaped target. Each space between spades is covered by a target electrode which provides a beam-receiving position or compartment. The spade adjacent the radial arm of the L-shaped target holds a beam on that target when the electrodes are connected to appropriate circuitry and voltages. The switching grid and spade on tne other side or the space serve to move the beam toward them and into the next compartment to strike the next target.

'lnese tubes require an axial magnetic field permeating them. For the beam to move in a clockwise direction the magnetic flux lines must flow toward the observer. This axial magnetic field usually is provided by a cylindrical permanent magnet but could be provided by an electromagnet or a combination of both type magnets. when a positive potential with respect to the cathode is applied to the spade electrodes and target electrodes,

crossed-magnet electrical fields of a magnetron are provided. in this invention these fields are adjusted to place the tube well into the magnetron cut-off region, so no beam is formed and no current flows when the potential of all spades is positive. If the potential of one of the spades is lowered to near the cathode potential, this axially symmetrical field is changed and electrons will flow to the compartment adjacent this spade, forming a beam. Some electrons strike this spade and flow through one of the resistors which connect each spade to the positive potential. The resulting 1R voltage drop developed by current flowing through the resistor enables tnat spade to hold the beam stably in that compartment, striking the target thereof. To switch this beam to the next compartment, the switching electrode in the compartment holding the beam is given a low potential. This alters the beam so that at least some of it moves toward this switching electrode and the spade electrode near it. When some of the beams current flows through this next spade a voltage drop occurs due to this current flowing through a resistance connecting this second spade to its positive potential. This voltage change causes the beam to swing on into the next compartment and enables the next spade to hold the beam in position.

In accordance with the features of one embodiment of this invention, the target electrode of the last array in a first beam switching tube is connected to the voltage supply through a resistor which also connects the first v spade electrode of the succeeding tube to this voltage supply. Impingement of the beam upon the target of the last array causes an electron current to flow through the resistor mutually connecting the first spade and last target to the voltage supply and this lowers the potential on the first spade electrode of the normally cut-ofi succeeding tube enough to form a beam at the first array thereof. In this manner, only one array or position of each tube is used as a control position for beam extinguishing and forming, and nine positions are available for useful output positions in each. tube. The spade load 3 resistor-for this control position is made too low in ohmic value to stably hold the beam when the beam is switched thereto. Accordingly when the control position is reached, the beam is cutofi in eachtube.

The various features of the invention will .be. more fully understood from thefollowingldetailed. description and the accompanyingdrawings, in whichif V Fig. 1 is a' circuit diagram including'a plan viewof the electrodes in a magnetron beam..s'witching magma,

Fig.2 isia schematic diagram of multiposition switchingcircuit embodying the invention' 7 4 V V V In Fig. v1,'a plan view of theelectrodes within a magnetron beam switchingftube. areshown. Thefc'entral cathode K defines the axis .of. theitub'e, and the magnetic field v 1a is established with lines through the tube parallel to the axis,"with lines proceeding'from the plane in the drawing tofcause' clockwise rotation of the' beamduring switching. The generally 'U shaped spade electrodes S10 to S19 are arranged concentrically around the cathode with their convex surface" facing the cathode. The rodlike 'switchinggrids G10t'o G19 are positioned concentrically around/cathode K, onia radius slightly larg r than that for the-spades, and each grid is radially aligned with one edgeof a corresponding spade. The L -shaped target electrodes T10 to T19 are arranged with their circumferential portions on a radius slightly larger than that for the switching grids, andv with radial surfaces extending into the concave portion of the associated spade. One set of electrodes, such as target T10. grid G1 0, and spade S10 are considered a group providing one outnut position. 'Thisparticular group is designated as an initial position. Each of the spade electrodes is connected to a voltage E 'through a corresponding, resistor R To simplify the drawing, only representative connections are shown. Each of thetargets except target T19 is connected to a voltage E through acorrespondingre, sistor' RL Target T19 is termed the last target since it is thelast. target to receive the beam before another cycle starts on target T10. Target 19 couples. the tube to a'following similar tube atthe junction of resistors R and R used for connecting the initiaLspade. S10. of the following tube tovoltage E It is a characteristic of suchnmagnetron. .type tubes that, with the cathode to-spade voltage and axialmagnetic field adjustedbeyond a critical ratio,.no current will flow to the targets. ,If, however, the voltage on one of thespade electrodes is lowered, the circumferentially symmetrieelectiicahfield gradient within the tube :is changed and electrons will movealong equipctential lines, forming a radially extendingheamc To initiatebearn formation when thebeamisecutgoff,:the beamtorming switch 30 may beactuated to., lower .thespade potential momentarily to ground potential. .This beam will curve outward'to grazethespade. electrode having a loweredpotential andstn'kethe adjacent targetelectrode. With a resistorR of the proper value in series with each spade, the slight portign .of the beam current which strikes the spade itgrazesis causedtodepress thatspades potential due to the beam current flowing through-the.

resistor R This etfect enables a spade to holdthe beam in a stable lock-in .positioncnce the beamhas been formed on the. associatedzarray. I a a Toswitch a beam frorncne set of electrodes to another,: switching grids G10to G19-are provided in each- In one circuit connec ion, switching grids G10' Thus,.alternate sets of grids receive the-suecessive'nega tive pulses of a switching signal;

Consider the moment -when a beam is formedon:

. 4 V 7 target T10 and grid G10 of tube A is driven to a negative potential. Because of'the change this introduces in the equipotential lines between spades S10 and S11, the beam potential through a negative going pulse on lead .21.

moves toward spade S11 and a small amount of beam current strikes spade $11. The flow of this current through spade S11s resistor R lowers the potential of spade S11 producing additional change of the electrical field which causes the beam to switch to target T11. At this momentgrid G11 is not negative and may even be at a positive potential when a sinusoidal switching signal is used. Thus, no further switching occurs at that moment. On the next half cycle of a sinusoidal switching signal oruponthe next pulse from the flip-fiop-circuit or other source of push pull switching signals, grid G11 will be driven negative and another switching step occurs as for grid G10. The alternate connections limit the switching to a single step for each half cycle of the switching signal. V V J In .l-"gi g. 2, two, ten-array, magnetron beam-switching tubes, A and B, are shown for clarityina linearly disposed form. T-hetubes. are coupled for stepping through eighteensuccessive positions. To simplify the presentation, representative:connectionsare made in the drawings to indicate that the manner in which a number of elements may be similarly connected. Thus spades S111 to S18 are connected through separate resistors R to voltage V and targetsfTltl to; T18-are connected through. resistors R 'to voltage V Initial spade S10 of each tube has resistors R and; R of total series resistance;

equal to.R connecting it to voltage V and the last spade S19 of each tube hasresistor-R of lower ohmic value .than R 'conneeting it to voltage V TargetT19 of each tube ;connec ts ;to-the junction, point between resistors R and .R gof the seriesconnection to spadeS10. of; the followingtube. I cathodes K; aregrounded or con-.

at t a rt e at ve ta VK- To start the pulse distributigymthe potentialon initial spade 5100i tube A is lowered to'about ground potential: Switch 30 can be nscd, for anfinitiating negative trigger pulse could beproyided at the same point. This lowered potential on spade S10 of tube A causes a beam to .forrn.

to initial;target*110;. A smalliportionjof this beam current.- strikes rspade S10 and thevoltage drop it produces gnidsofi-tube; B; connect to lead 21.. and .the,..even..grid-' of tube B connect to lead 20. This transportation of. connections will.-be explained in connection. with the switching. sequence [through both. tubeA and tube B;

Consider :the moment. when abearn is formed vontarget T10 'of'tube A and grid G10 of :.tube A is driven to a low Becauseof the change this introduces in :theequipotential lines within tube A, the beam. will switch overv spade S11 to striketarget'T 11. Since no signal, or. an opposite positive signal, has; been applied lto' grid G11 at this moment theheamewilhnot progress any further. the-.next half :cycle of the switching signal a negative pulse .isappliedzon lead 20sand grid G11 does go negative" causing :the, beam .)to advance overjspade 12' to strike target T12. ascdescrib ed before. -This switching sequence continues withzeackhalf cycle of the switc'hingsignal through the; positions of tube A until the beam. reaches thelast targettT19. "Here the flow of beamcurrent fromtarget 1 T19; goes through resistor R1. of: the. next; tube :13

lowering :the potential; of I initialfspade S10; thereby caus- .inga beam toi-formilin tube B. .At .the same: time, only the.smallsfracticnio-tx the heamucurrent striking spade S19 zflows through resistor R3. However, resistor" R3 1 neat 359e is of too low an ohmic value to enable spade S19s potential to lower enough due to the IR voltage drop caused by the flowing through resistor R3, to enable spade S19 to hold the beam stably on target T19. Accordingly, the beam in tube A is extinguished shortly after it reaches the electrode group comprising target T19 and spade S19. Where useful values for R are in the order of 100,000 ohms, the useful values for R have been found to be in the order of 40,000 ohms.

With an odd number of useful output positions per tube (positions to 8), grid connections in the next tube B must be transposed in order to maintain an uninterrupted switching sequence. Consider tube A to be the first tube and tube B to be the second, etc. Accordingly, the push-pull output of the flip-flop pulse generator 29 shown in Fig. 2 has the odd grids of all odd tubes and the even grids of all even tubes coupled to one output connector 21, and the even grids of all odd tubes and the odd grids of all even tubes coupled to the other output connector 20. The need for this will be evident from the following description.

If the switching sequence and transfer from one tube to the other is considered in connection with Fig. 2, it will be seen that the above explained pattern of grid connections is required. When the beam reaches target T18, a pulse on the even grids of the odd tubes will be applied to grid G18 causing the beam to switch to target T19. Spade S19 is connected to voltage V through resistor R which is of too low an ohmic value to enable spade S19 to hold the beam, so tube A is cut oif. However, for the short period when the beam is on target T19, beam current flows through resistor R of tube B and lowers the potential onspade S of tube B. This forms a new beam on target T10 of tube B. Now, the next pulse must be applied to the even grids of the even tubes B etc. in order to switch the beam in tube B from target T10 to target T11. The other grids of both tubes must be connected to maintain the alter nate relationship that has been described.

As the switching beam progresses through tube B, it reaches target T18 thereof, and the next switching signal moves the beam to target T19. In the same manner described for tube A, the connection of spade S19 through resistor R renders spade S19 of tube B incapable of holding the beam stably on target T19 so tube B cuts off when this electrode group is reached. The electron current flow to target T19 of tube B is conducted through resistor R1 to voltage source V This current flow causes a negative pulse on spade S10 of tube A, forming a new beam in tube A before tube B cuts off. It is within the scope of this invention to make the connections from tube B to another succeeding tube instead of returning the sequence to tube A or to allow it to eX- pire until a further cycle is initiated by switch 30. The succession can be extended to a large number, N, of ten position tubes, providing 9N output positions for each sequential tube connection.

In all the tubes, targets T10 to T18 inclusive are the switching positions connected to output circuitry. Switching signals advance the beam to these targets in succession and from tube to tube. Instead of common connections of alternate grids utilizing push-pull switching signals, all grids can be coupled in one common connection. The switching signals therefor would be pulses of such timed duration and amplitude that only one step of the beams advance is possible during each pulse.

Switching achieved through potential gradient changes produced by voltages applied to the switching grids is not the only method by which the beam can be switched in a beam switching tube. Alternate methods are known, such as depressing the potential of the cathode so that the spade-to-cathode potential is increased, or increasing the potential simultaneously on all the spades to achieve the same effect. When such alternate switching ethcds are employed, tubes without switching grids may *6 be utilized or switching grids may be biased to some lieu tral potential which permits the tube to function.

If a repetitive cycle is not desired, as mentioned hereinbefore, then the last target 29 of the last tube in a succession of tubes would be connected through a resistor R to voltage supply V as are all other targets, and there would be no connection to .the initial spade 510 of the first tube. Thus, with low ohmic resistor R3 in series with spade S19 of this last position, the beam could not be held on target 29 and the last tube would be cut off. Switch 30 would then be actuated to start another cycle.

A flexible electronic switching system thus has been provided, capable of utilizing all but one position of each beam switching tube for useful output positions and equally capable of being connected for fewer positions or of being connected back to an initial position for repetitive cycles through the succession of beam tubes.

What is claimed is: I

1. An electron beam switching system comprising a succession of magnetron beam switching tubes including at least an initial and a last tube in said succession of tubes each tube having a cathode and a multiplicity of spade electrodes, switching grid electrodes, and target electrodes arranged in a succession of electrode groups of one of each said electrodesper group, with one group starting said succession of groups and designated the initial group and another group at the other end of the succession designated the last group, circuit means for connecting said magnetron beam switching tubes to a voltage supply and including first resistance means connecting each target electrode except the last target electrode of each tube to a voltage supply to receive electron beam currentand second resistance means connecting each spade electrode except the last spade electrode of each tube to a voltage supply to pass enough beam current to hold a beam in place when it reaches the respective electrode group thereof, starting means to lower the potential on the initial spade electrode of the initial tube to form a beam to the initial electrode group, coupling means connecting the last target electrode of each tube with the initial spade electrode of the following tube to lower the potential of said initial spade when an electron beam strikes said last target thereby to form a beam in said following tube, third resistance means for connecting the last spade of each tube to a voltage supply enabling said last spade to cut oil. a beam when the beam is switched to said last group, and switching means connected to said switching grid electrodes to advance a beam to each electrode group of a tube in succession and from tube to tube in said succession of tubes.

2. A pulse distributor comprising a plurality of normally cut-ofi magnetron beam switching tubes each having a plurality of beam forming and holding electrodes, switching grids, and output electrodes arranged in successive electrode groups, starting means connected to a spade electrode for forming a beam in one of said plurality of tubes, circuit means connecting a target electrode of each tube with a spade electrode of a following tube of said plurality and responsive to a beam striking said target electrode to form a beam in said following tube of said plurality of tubes, and switching means connected to said switching grids and responsive to switching signals to advance a beam successively to the electrode groups of each tube and from tube to tube in succession.

3. In an electronic switching system a succession of multiple output beam switching tubes each being normally cut-off and having a plurality of beam receiving compartments each comprising a spade electrode, a grid electrode, and a target electrode, circuit means interconnecting a target electrode of each tube with a spade electrode of a following tube resistive means in said circuit means responsive to a beam striking saidtarget electrode of the transferor tube to-cause the potential of said spade electrode to decrease and a beam to form to 7 multipleoutput beam switchi'rrgftubes eachhaying a'plurality of beamreceiving compartments each comprising a spade electrode, a; electrode, and a. target electrode, circuit means interconnecting a target "electrode'j'ofjeach tube with a spade electrodeof'afollowing tube, a resistor commonly connected withthe interconnected spade and target responsive to a beam striking'saidYargefelectrode of'the transfer-or tube to' cause thepotential ofsaid'spade electrode to drop; and; a beam to form to the compartment of 4 the "transferee; be", having Said spade: electrode, and cifcuitflm'eans coupled to. "the spade electrode of the compartment of each tube having saidinte'rconnected target electrode toQeXtinguish the beam ofjach. tubewhen the beam reachestsaid'compartment.t t f 5. In an electronicbeam'switching system a succession of magnetrontbeam switching, positions having aplurality of arrays for successively receiving the beam and each array having at least aspade electrode and a target electrode, circuit'means coupling, the target electrode of a predetermined array with. the spade electrode of afurther successive array to form abeam at said successive array, and current responsive meansconnectedfor'applying potential to an electrode of said predetermined array so that it will cut oil the beam shortlyafter said beam: reaches said predetermined: array.

6. A circuit as defined-in claim wherein said current responsive means 'is inthe beam current-path-of said predetermined arrayand-will'cut off the beam shortly after said beam reaches-said predetermined array.

7. An electronbeamswitching system comprising, a succession of magnetron beam switching tubes, with each tube including a plurality of electrode groups for successively receiving a beannand each group having a spade electrode and a targetelectrode and defining a beamreceiving position, starting means connected to .the spade electrode ofqthefirst; group, of the first tube of said succession to form a'beam directedlintosaid-first group, im pedance means to connecteach spade'electrode and target electrode except thosezof the last group of each tube to a. voltage sourceto holdithe electronbeam of their respective tubes on their respcctiveggroup. when thelbeam is switched thereto, current responsive means connected to thelast group ofeach tube to couple the target electrode 'of said last group toithespad'e electrode of the following tube to .form a beam in said following tube and to control the potential-of thespade electrode of said lastgroup to cut off the beam in each tube when the beam is switched to said' last group ofeach tube, and an input circuit connected to electrodes of said tubes and responsive to switching signals to cause a beam to advance to successive'groups and to successive tubes in smooth transition.

8. An electron beam switching system comprising a plurality of cutoff magnetron beam switching tubes with each tube having at least a cathode, N spade electrodes and N output electrodes, said spade electrodes and output electrodes being -'-arranged in groups of one of each type electrode pergroup toprovide' N elect-rode groups, coupling circuit means between successive'tubes interconnecting an output groupof each tube with an input group of a following" tube, current responsive circuit means connected toeach output group to extinguish a beam when it-reaches-said output group,-means for starting a beam in a tube of said plurality'of tubes, andmeans for successively's'tepping the beam to deliver continuoususeful output indications at'N -l. electrode groups in each tubein 11651101156 to the beams" stepping: succession.

9. ,A .multistable position magnetronbeamtube switch and" holding i a beam" in stable position; when -rece ing s ys'tem comprising a in ates of electrode: groups each comprisip'g e a spade ;electrodefor-;forming '21? Beam beam cu-rrent, means' fOrTdEflmting' a beam from e stabIeposi-t-ionto th'e next, and a tar get"electrodeitoifreceiving bean}currenttoroperatingioadl ircnitjs; with one; grasptartin said succession of groups? and'designatd the initial' grouoand anothergroup at the otheren'dof the succession -anddesignafed thelasbgroup', circuit means for connecting the magnetionfbeanr tube; to 'a voltage supply and infcluding iiisf resistance *mean'siconnect: ingeach targetfele'ctrode excavate last ta rget' electrode to s voltagef-supply'to receive el'ebtron beam currentand second resistance meansconnecting each spad e electrode exeejat-thlit spade "electrode-to avolta-ge supplyt'o pass enoughb earn-{current to hold a -beaIrr-in place" when-it reaches the respective electrode group-thereofimeans for operating the elect-rode grbup's' irr magnetron cut" oifcond-itions,'-starting'nreans to lowerthepotentialbn aspade electrode to former beam irr the correspondingel ectrode group, coupling means for-connecting a beamreceiving theelectrod-e'i'n the lasteIect-rode group with a spade elec trode in an'initial-group to lower the potential of said,

spade electrode of "the-initialgroup when-an electron beamstrikes the last target therebyto-form-a b'eamat'the respective electrode group,*-third'resistance means for' connecting-the spade of-the last group to a voltage supply enabling said' last-sp'ade-tocut 01f a-beam shortly'after' the b'eam is switchedto saidlast group, andswitching signal means connected tothe means for deflecting a beam from one' stable position to'th'e next, to advance a beam" from one "electrode group to another along said succession of groups.

10. An electron beam switching system comprising a succession of magnetron beam switching tubes including" atl'east an initial and a lasttube, each tube having a cathode, amultiplicity of spad'e electrodes f'or forrnin'g and holding a beam, switching grid electrodes and. target electrodes arranged in a succession of elect-rode groups ar one oi:' each fsaid' electrodes per group, with one' group starting-said succession of groups and designated the initial groupythe intermediate groups numbered successively, and another group at the other end of the succession designated the last group, circuit means for connecting said magnetron beam switching tubes to a voltage supply and including first resistance means connecting each target electrode except the lasttarget electrode of, each tube to avoltage supply to receive electron beam current and second resistance meansfconnectingeach,

spade electrode except the'last, spade electrode of each are developed respectively connected to sets of alternately disposed switching electrodes in each tube comprising odd numbered and even numbered switching electrodes, the sets ofleven numbered electrodes of each tube being connected to the same switching. means lead with the sets of odd numbered electrodes 'of adjacent switching tubesin said succession.

References Cited in the file of this ,patent j UNITED, STATES PATENTS 7 2,568,177 Vroo'rn L. .Sept. 18,1951 2,652,514 Davison Sept. 15', 1953f 2,721,955 Oct.;-25, "19 5-5 

